Polyethylene terephthalate (PET) is widely used as an extrusion and injection-molding resin for the fabrication of various articles for household or industrial use, including appliance parts, containers, and auto parts. Because many of such articles must withstand considerable temperature changes and/or physical abuse, it is customary to blend polyethylene terephthalate with other polymers, such as ionic copolymers of alpha-olefins and polyolefins, to improve its impact resistance as shown by notched Izod impact values. There are advantages, however, in keeping PET as the matrix material in PET/polymer blends and those are to retain tensile strength, flexural modulus, elongation percent, weather resistance and heat deflection temperature.
Polymer blends of PET with polyesters or copolyesters containing 1,4-cyclohexanedimethanol (CHDM) are disclosed in U.S. Pat. Nos. 4,263,364 and 4,897,448, and in Research Disclosure No. 25244. U.S. Pat. No. 4,263,364 discloses reinforced stampable multi-layer sheets prepared from blends of PET and copolymers of poly(1,4-cyclohexylenedimethylene terephthalate). The blends are limited to blends of PET or PCT with greater than 35 weight percent of either copolymers of PET having 5-50 mole percent CHDM, or copolymers of PCT having 20-50 mole percent ethylene glycol.
U.S. Pat. No. 4,897,448 discloses impact modified polyester-polycarbonate blends containing a polyethylene terephthalate type polyester, a poly(1,4-cyclohexylene-dimethylene terephthalate) type polyester, a polycarbonate, and an impact modifier selected from ethylene-propylene rubbers and acrylic core-shell polymers. Research Disclosure No. 25244 discloses blending two polyethylene terephthalate polyesters which are modified with a different mole percent of 1,4-cyclohexanedimethanol.
In contrast, the present inventors have unexpectedly discovered high impact strength films and articles obtained from polyester blends containing polyethylene terephthalate and 1 to 12 weight percent of a polyester or copolyester which contains at least 30 mole percent 1,4-cyclohexanedimethanol.